# -*- coding: utf-8 -*-
"""
Created on Wed Jul 26 13:10:20 2017

@author: lilin
"""

import pygame
from pygame.sprite import Sprite

class Ship(Sprite):
    
    def __init__(self,ai_settings,screen):
        """初始化飞船并设置其初始位置"""
        super(Ship,self).__init__()
        self.screen=screen
        self.ai_settings=ai_settings
        
        #加载飞船图像并获取其外接矩形
        self.image=pygame.image.load('images/ship.bmp')
        self.rect=self.image.get_rect()
        self.screen_rect=screen.get_rect()
        
        #并将每艘飞船放在屏幕底部中央
        self.rect.centerx=self.screen_rect.centerx
        self.rect.bottom=self.screen_rect.bottom
        
        #在飞船的属性center中存储小数值
        self.center=float(self.rect.centerx)
        
        #移动标志
        self.moving_right=False
        self.moving_left=False
        
    def update(self):
        """根据移动标志调整飞船的位置"""
        #更新center值而不是rect
        if self.moving_right and self.rect.right < self.screen_rect.right:
            self.center +=self.ai_settings.ship_speed_factor
        if self.moving_left and self.rect.left > 0:
            self.center -=self.ai_settings.ship_speed_factor
            
        #根据self.center更新rect对象
        self.rect.centerx=self.center
        
    def blitme(self):
        """在指定的位置绘制飞船"""
        self.screen.blit(self.image,self.rect)
        
    def center_ship(self):
        """让飞船在屏幕居中"""
        self.center = self.screen_rect.centerx
    
    
    